1. Field of the Invention
The present invention relates to a system for stretching and severing a strip-like resin sheet, and more particularly to a system for stretching a strip-like resin sheet into a fan shape and thereafter cutting off the sheet to prescribed dimensions.
2. Description of the Relevant Art
Recent automotive windshields are made up of laminated glass comprising two glass sheets bonded together with an intermediate film of polyvinyl butyral therebetween.
The intermediate film is produced by cutting off a strip-like resin sheet having a constant width. Such a strip-like resin sheet may be severed to the same shape as the overall shape of desired laminated glass, but any resulting scraps will be useless. If the strip-like resin sheet to be cut off includes a glare-resistant gradient band on one side thereof, the gradient band will be cut off so that it will have different widths at its center and opposite ends at the time of severing the strip-like resin sheet.
Japanese Patent Publication No. 53-16027 published May 29, 1987 discloses an apparatus for heat-softening a strip-like resin sheet unwound from a sheet roll, then stretching the sheet to a fan shape on a conical drum, and finally cutting off the fan-shaped sheet to the entire shape of automotive laminated glass. According to the disclosed apparatus, the resin sheet can efficiently be cut off and used.
However, the disclosed appararus is poor in its efficiency since the resin sheet is cut off manually. More specifically, the fan-shaped resin sheet as it leaves the conical drum is delivered onto a base table and then cut off by a manually operated cutting machine to a desired shape which is used as an intermediate film. The intermediate film is then manually stacked on a stock table. Therefore, two workers are needed to operate the cutting machine and to stack the severed intermediate film. The manual cutting process tends to develop errors with respect to the dimensions of the severed intermediate film. The manual stacking procedure is liable to cause the intermediate film to be wrinkled when it is stacked.
In apparatus for cutting off strip-like resin sheets to given shape, which may include the aforesaid disclosed apparatus, the resin sheet is pulled from a sheet roll by pinch rollers and then cut off. For continuous operation, when the resin sheet from one sheet roll is consumed, the leading edge of the resin sheet from another sheet roll must be spliced to the trailing end of the resin sheet in use. Heretofore, the splicing process has been effected manually. In the manual splicing process, alcohol is first applied by the worker to the trailing end of the preceding resin sheet, the leading end of the next resin sheet is placed on the trailing end of the preceding resin sheet, and then the overlapping ends of the resin sheets are manually pressed together to join the resin sheets. The manual splicing procedure is therefore complex and low in efficiency, and also requires an air ventilation system.
The present invention has been made in an effort to eliminate the aforesaid drawbacks of the conventional apparatus for stretching and severing a strip-like resin sheet.